Grooved plywood facing



May 6 941- M. H. CARPENTER 2,241,080

` @www PLYwoUD FAcING Filed sept. 7, 1940 Q lNVENTOR ATTORNEYS mental Mey 6,1941

2,241,030 Gaoovnn rLYwoon'FAcxNG Miles H. Carpenter, Merrick, N. Y., assignor to Dura-more Buildings, Inc., Brooklyn,

N. Y., a

corporation of New York Application :September 7, 1940, Serial No. 355,733

1 Claim'.

Plywood panels have many advantages for exterior building facing, including lightness, cheapness and strength. However, either aesthetic considerations or habitual prejudice cause many persons to dislike a smooth, ilat expanse, particularly on residential buildings. In order to suit the requirements of many purchasers, the exterior walls must be iinished `in clapboarding or material givinglthe same visual effect.

The outstanding visual feature of clapboarding is the horizontal lines delineated by the joints and which stand o ut as shadow lines due to the grooves left by the overlapping or partially overlapping ends of the clapboards. In the case of panels ot solid lumber it would be comparatively easy to form grooves to give the same visual effect as the clapboard. joints. In the case of plywood, however, the strength of the composite panel 'depends directly on the number of builtup layers. With alternate layers having their grains extending at right angles to each other,

as is usual, the layer or lamination whose grain extends in one direction imparts certain elements of strength to the panel andwithstands certain strains while other elements oi' strength are im parted and other strains withstood by the laminations .whose grain runs in the opposite direction.

The forces of strain are particularly resisted' by the joints between the laminations. Ii the bond between the laminations is broken, then a material portion of the strength of the panel is lost, this being somewhat critical at each plane of bond. For example, a cut half way through one of the laminations will reduce the strength somewhat. A cut all the way through one of the laminations which thereby breaks the bond at the point where the grains run in oppositedlrections will reduce the strength more than twice as much as the original cut.

When providing grooves in a laminated plywood panel, two opposing and more or less incompatible requirements must be met. The groove must he pronounced enough to give a reasonably prominent horizontal line apparent` to the eye, and at the same time the groove must (Cl. 2li-91) In the accompanying drawing,

Fig. 1 is an end view of a portion oi a panel provided with shadow line grooves` in accordance with my invention;

Fig'. 2 is a front view thereotwith successive laminations broken away; and y Fig. 3 is an enlarged detail of a portion of Fig. l.

The plywood panel III is composed oi more than one laminati'op of plywood, in this instance ilve lamlnations, I2, I4, II, I2 and 20. The grains of alternate laminations run in opposite directions. In the form shown the grains of 1aminations I2, I8 and 20 run horizontally, while the -grains oi' laminations I4 and I8 run vertically.

` In 'the face lamination I2, grooves 22, 22 are cut. It is to be noted that these grooves are parallel tqeach other and parallel to the general grain direction in the i'ace lamination I2 in which they are formed. The grooves 22 extend into the lamination I2 to a material extent but less than the whole thickness of this lamination. Thus they do not cut the joint I2 between laminations I2 and Il but leave the inner surface of the lamination I2 in continuous unbroken bonded contact with the adjacent face of lamination Il. Preferably the grooves 22 are cut in to a depth of about two-thirds the thickness of the face lamnot extend deeply into the plywood panel because doing so would tend to impair the strength of the panel and require that a thicker and therefore more expensive panel be used.

The present invention resolves these two apparently incompatible requirements in that it produces a pronounced shadow line and leaves.

the panel with practically its entire original strength. v

ination. l o The grooves 22 are formed with their upper sides 24 extending in horizontally at right angles lto the face of the panel. The lower sides 26 slant downwardly and outwardly and the width is preferably about four times as great as the Width of the upper side 2l.

The strength of the composite panel in a vertical direction is concentrated principally in vertically grained Vlaminations I4 and I8, while the strength in a horizontal direction is concentrated principally in horizontally grained laminations I2, I8 and 20. Inasmuch as each individual lamination contributes very little strength across its grain, the strength which face lamination I2 contributes, and the total strength of the composite panel, are not materially atlected by the grooves 22 which run generally parallel to each other and to the grain of the lamination in which they are formed. The strength of this lamination I2 in the direction oi.' its grain is substantially unimpaired, being affected only to the extent of 1 or 2%, or the like, and its strength in a vertical cross grain direction is comparatively little in any event, and'therefore weakening in this regard does not materially affect the strength of the composite panel.

By having the upper side of groove 22 cut in sharp at a right angle, a sharp and pronounced shadow line from the light of the sky is achieved, while the tapered lower side of the groove provides a broadening of the shadow as seen by the eye, and at the same time water 'and dirt wash right down the sloping lower surface instead of lodging in the groove. Because the inner face of the lamination I2 where it is bonded to the adjacent lamination I d is left continuous and unbroken, the building up of composite strength between these two laminations which actin opposite directions is not impaired. No breaks are provided where creeping or splitting could achieve a concentrated start. Likewise the bond itself is not exposed to be weakened byl air. sunlight or the entry of water. In spite of the fact that I have made a series ofrcuts of substantial depth into the face of the panel and secured a prominent series of shadow lines, the strength and durability of the panel/are'not impaired to any material degree.

Having thus described a preferred embodiment oi' my invention, what I claim is:

A shadow-lined plywood facing panel comprising a plurality oi.' bonded together wood laminatio'ns, the grains oi' adjacent laminations e'xtending at right angles to each other, a plurality of grooves in the outermost of the laminations, said grooves being spaced-apart and parallel to each other to simulate weatherboarding, and parallel to the grain of the wood in said outermost lamina, said grooves extending through a substantial part of the thickness of the outer lamina but to a depth ot less than its full thickness, whereby the bond between the outermost 

